Engineering Phase Stability of Semimetallic MoS 2 Monolayers for Sustainable Electrocatalytic Hydrogen Production.

1T'-phase MoS 2 possesses excellent electrocatalytic performance, but due to the instability of the thermodynamic metastable phase, its actual electrocatalytic effect is seriously limited. Here, we report a wet-chemical synthesis strategy for constructing rGO/1T'-MoS 2 /CeO 2 heterostructures to improve the phase stability of metastable 1T' phase MoS 2 monolayers. Importantly, the rGO/1T'-MoS 2 /CeO 2 heterostructure exhibits excellent electrocatalytic hydrogen evolution reaction (HER) performance, which is much better than the 1T'-MoS 2 monolayers. The synergistic effects between CeO 2 nanoparticles (NPs) and 1T'-MoS 2 monolayers were systematically investigated. 1T'-MoS 2 monolayers combined with the cocatalyst of CeO 2 NPs can produce lattice strain and distortion on 1T'-MoS 2 monolayers, which can tune the energy band structure, charge transfer, and energy barriers of hydrogen atom adsorption (Δ E H ), leading to promotion of the phase activity and stability of 1T'-MoS 2 monolayers for hydrogen production. Our work offers a feasible method for the preparation of efficient HER electrocatalysts based on the engineering phase stability of metastable materials.